This invention is in the field of ventilation. More particularly, the invention relates to a wall ventilation screen that permits airflow but simultaneously prevents rain water other elements from penetrating into buildings or vehicles.
There are numerous circumstances when it is desirable to keep a flow of fresh air while protecting the interior of a building, vehicle, canopy, tent, shelter (equipment, plants, animals or human shelter), or personal enclosure from rain and other adverse natural or man-made elements including noise, light, or sand.
There are two important characteristics that define a ventilation device performance. The first is permitting an adequate air flow. The second is protecting against rain water, sand, noise and other elements. The establishment of an adequate air flow depends among other factors on the proportion of area that is not constricted by the devices' structures and their shapes, usually called “free area”. Those skilled in the art know that the air flow capacity of louvers or other ventilation devices is measured by the air pressure drop across the device. It is obvious for those skilled in the art that a design consideration should include minimizing this pressure drop.
The most commonly used devices for building ventilation are louver or damper vents. A louver is a window blind or shutter with parallel and generally horizontal slats. In louvers, the slats typically have a fixed angle in relation to air flow. Dampers consist of a movable plate, valve or parallel slats that regulate the air flow. Water-proof or storm-proof louvers provide some protection against rain water under weather conditions with little or no wind. However, when air velocity is above 5 m/s (1000 fpm), currently known louvers tend to allow significant water penetration. In louvers the protection against other environmental elements is also limited.
Dampers present structures for the regulation of air flow, and assist in preventing rain water from penetrating under storm conditions. However, structures with dampers are relatively expensive and need human intervention or expensive sensor-activated mechanisms to close and open the slats or regulate the air flow.
In general, such previous ventilation devices suffer from lack of efficiency in preventing the penetration of wind-driven rain water, or from high cost.
Another approach to protecting enclosures from rain water and simultaneously allowing some air permeability is based on panels of material made from porous membranes. For example, air-permeable membranes exist for use as rain screens in building walls and roofs. These materials certainly provide protection from rain water to internal building structures, but the air circulation through those membranes is generally insufficient to provide fresh air to spaces occupied by persons, animals or plants. Additionally, those membranes are not resistant enough to be exposed to the external weather for long time.